The Applicant's Patent Publication No. WO98/20446 discloses a reading pen which can be used for recording text by imaging this from a base. The reading pen has an optical sensor which records a number of images, with partially overlapping contents, of the text which is to be recorded. In addition, the reading pen has a processor which puts together the images, identifies the text in the images and stores it in character-coded format. The text can then be transferred to a computer with which the reading pen communicates.
In addition, the Applicant's Patent Publication No. WO99/60469 discloses an optical mouse which is arranged to position a cursor on a display of a computer.
The reading pen and the optical mouse are two examples of input units which can be used to input information into a computer and to control the function of a computer. Another example of an input unit is a keyboard, which can be used both to enter information and to control the computer by means of various keyboard commands.
A user does not want to have to change between different input units in order to be able to carry out different functions. Therefore it is a general requirement that each input unit is to be able to be used for as many different functions as possible and in no flexible and simple a way as possible for the user.
U.S. Pat. No. 5,932,863 discloses an arrangement for accessing electronic information via printed matter. More specifically, the arrangement comprises an input unit which via a keypad is switchable between a scanner mode and a mouse mode. In the scanner mode, a user can input an image of a dedicated object on the base, more specifically a bar code, a character or a symbol. The image is transferred from the input unit to a computer, which decodes the image and which, as a result, executes a preprogrammed command, for instance to obtain interactive software from an external database and executing this software on the computer. During execution, the user can, by operating the keypad, change the input unit to the mouse mode in order to interact with the software on a display.
A problem of inputting this type of dedicated objects is that the object must in many cases be accompanied by some sort of explanatory text, so that the user can understand which command is initiated by the object. In spacious order catalogues this can usually be provided, but in many other cases the space is more restricted. Therefore the user may have to learn to what each object relates, which however reduces the usability of the arrangement if it is to be generalized beyond a certain application, such as programming a television set.